JP2936746B2 - Engine evaporative fuel control system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel vapor control system for an engine in which fuel vapor generated from a fuel tank of a vehicle is guided to a combustion chamber to regulate fuel vapor released into the atmosphere.

[0002]

2. Description of the Related Art Since the emission of evaporated fuel from a fuel tank of an automobile to the atmosphere as it is causes air pollution, the evaporated fuel is introduced into an intake passage of an engine and burned together with supplied fuel in a combustion chamber. A device for causing this to occur is known. In these devices, the evaporated fuel is guided to a container containing an adsorbent such as activated carbon, and the evaporated fuel is temporarily adsorbed by the adsorbent. The evaporated fuel adsorbed by the adsorbent is released from the adsorbent by the negative pressure of the intake pipe during operation of the engine, and is introduced into the combustion chamber together with the intake air.

[0003] As examples of the prior art relating to the evaporative fuel control device, Japanese Utility Model Publication No. Sho 61-23644 and Japanese Patent Publication No. Sho 62-18747 are known. The former controls the purge flow rate of the evaporated fuel by duty-controlling the solenoid valve according to the amount of intake air per one revolution of the engine. The latter is one in which the evaporative fuel system is applied to a supercharged engine, in which adsorbed fuel is efficiently processed in a supercharging region. As mentioned above,
In the conventional apparatus, the purge amount of the evaporated fuel is adjusted by controlling the duty of an electromagnetic valve disposed in a purge passage. This duty ratio is determined by two factors: an engine speed (NE) and an air amount per engine revolution (GN) . It was determined from a dimensional map.

[0004]

And only INVENTION Problems to be Solved] In the conventional method of performing the duty control of the solenoid valve purge amount of evaporative fuel, following problems were present. If accelerated depress the accelerator from the fully closed state of the throttle valve, the air flow meter, an intake amount of the volume fraction of the intake passage and the engine demand content of the intake air amount (intake pipe volume fraction) flows instantaneously,
As shown in FIG. 7, the amount of intake air (G
N) overshoots the predetermined value by the volume of the intake passage. Therefore, the engine speed (N
If the purge control of the evaporated fuel is performed based on E) and the intake air amount per one revolution of the engine (GN), the purge amount increases more than necessary. Therefore, the air-fuel ratio (A / F) becomes rough, and in extreme cases, there is a problem that engine stall or misfire occurs.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an evaporative fuel control device for an engine which can eliminate the influence of the amount of intake air corresponding to the volume of the intake passage during acceleration and prevent engine stall and misfire. I do.

[0006]

An evaporative fuel control device for an engine according to the present invention which achieves this object is as follows. A purge solenoid valve is provided in the middle of a purge passage that guides fuel vapor generated from the fuel tank to an intake passage downstream of the throttle valve, and the degree of opening of the purge solenoid valve is duty-controlled in accordance with the amount of intake air per engine revolution. in the evaporative fuel control system of Rue emissions <br/> Gin adjust the purge flow to the intake passage of fuel vapor by a throttle opening change amount detecting means for detecting an opening degree change amount of the throttle valve The delay time of the purge increase start is set in accordance with the magnitude of the opening change from the throttle opening change detecting means during acceleration.
After the elapse of the delay time, the opening of the purge solenoid valve is adjusted.
An evaporative fuel control system for an engine, comprising: a purge delay unit that increases .

[0007]

In the evaporative fuel control system for an engine constructed as described above, the throttle valve opening change amount is detected by the throttle opening change amount detecting means during acceleration .
This opening degree change amount signal is input to the purge delay means. The purge delay means calculates the delay time according to the opening change amount of the throttle valve at the time of acceleration, and delays the start of the purge increase of the evaporated fuel by the purge solenoid valve. for that reason,
During acceleration , the engine is not affected by the amount of intake air corresponding to the volume of the intake passage, and engine stall and misfire due to rough air-fuel ratio are prevented.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment of an engine fuel control system for an engine according to the present invention will be described below with reference to the drawings.
FIGS. 1 to 6 show one embodiment of the present invention, and particularly show a case where the present invention is applied to a six-cylinder engine mounted on a vehicle. 2 shows a system diagram of the engine centering on the evaporative fuel control device, and FIG. 3 shows a control system diagram of the engine excluding the evaporative fuel control device.
In FIG. 3, 1 indicates an engine, 2 indicates a surge tank, and 3 indicates an exhaust manifold. Exhaust manifold 3 is composed of # 1 to # 3 cylinder groups and # 4 to # 6 cylinder groups that do not involve exhaust interference.
And the assembly is communicated by the communication path 3a. Reference numerals 7 and 8 are a main turbocharger and a sub turbocharger arranged in parallel with each other. The respective turbines 7a, 8a of the turbochargers 7, 8 are connected to a collection portion of the exhaust manifold 3, and the respective compressors 7b, 8b are connected to the surge tank 2 via the intercooler 6 and the throttle valve 4.

The main turbocharger 7 is operated from a low intake air amount range to a high intake air amount region, and the sub turbocharger 8 is stopped in the low intake air amount region. In order to enable the operation and stoppage of both turbochargers 7, 8, an exhaust switching valve 1 is provided downstream of the turbine 8a of the sub-turbocharger 8.
7, an intake switching valve 18 is provided downstream of the compressor 8b. When both the intake and exhaust switching valves 18 and 17 are open, both turbochargers 7 and 8 are operated.

In the intake passage of the auxiliary turbocharger 8 stopped in the low intake air amount range, one turbocharger
In order to smoothly switch to the individual turbocharger, an intake bypass passage 13 that communicates between the upstream of the compressor 7b and the downstream of the compressor 8b, and an intake bypass valve 33 provided in the middle of the intake bypass passage 13 are provided. . The intake bypass valve 33 is a diaphragm type actuator 1
Opened and closed by 0. A check valve 12 is provided in a bypass passage communicating the upstream and downstream of the intake switching valve 18, and when the intake switching valve 18 is closed, the compressor outlet pressure on the sub turbocharger 8 side reduces the main turbocharger 7.
The air is allowed to flow from the upstream side to the downstream side when it becomes larger than the side. In the drawing, reference numeral 14 denotes an intake passage on the compressor outlet side, and reference numeral 15 denotes an intake passage on the compressor inlet side. The intake passage 15 is connected to an air cleaner 23 via an air flow meter 24. A front pipe 20 that forms an exhaust passage includes an exhaust gas catalyst 21,
22 is connected to the exhaust muffler. Intake switching valve 1
8 is opened and closed by an actuator 11, and the exhaust switching valve 17 is opened and closed by a diaphragm type actuator 16. Wastegate valve 31
Are opened and closed by an actuator 9.

Actuators 9, 10, 11, 16, 4
2 is activated by the introduction of a supercharging pressure or a negative pressure. Each actuator 9, 10, 11, 16,
In order to selectively switch between the supercharging pressure or the negative pressure from the positive pressure tank 51 and the atmospheric pressure from the downstream of the air flow meter 24, first, second, third, fourth, fifth, and Sixth
Of the electromagnetic valves 25, 26, 27, 28, 32, 44 are connected. Each solenoid valve 25, 26, 27, 28, 32, 4
The switching of No. 4 is performed according to a command from the engine control computer 29. The second solenoid valve 26
A check valve 45 that allows only one flow of the negative pressure is interposed in the passage for introducing the negative pressure into the passage.

When the first solenoid valve 25 is turned on, the intake switching valve 1 is turned on.
Actuator 11 is actuated so that 8 opens the valve,
When OFF, the actuator 11 is operated so that the intake switching valve 18 is fully closed. The ON of the fourth solenoid valve 28 activates the actuator 16 to fully open the exhaust switching valve 17, the OFF activates the actuator 10 to fully close the exhaust switching valve 17, and the OFF is the intake bypass valve 33. The actuator 10 is operated so as to fully open.

A fifth solenoid valve 32 for introducing atmospheric pressure to an actuator 42 for operating the exhaust bypass valve 41
N, not duty control but duty control. Similarly, the sixth solenoid valve 44 that guides a negative pressure to the actuator 9 that operates the wastegate valve 31 is turned on and off.
Duty control is performed instead of control. As is well known, the duty control is to control the energization time by the duty ratio, and the average current is variably controlled in an analog manner by digitally changing the ratio of energization and non-energization. The duty ratio is the ratio of the energizing time to the time of one cycle, and the energizing time in one cycle is A,
Assuming that the non-energization time is B, the duty ratio = A / (A +
B) × 100 (%). In the present embodiment, the fifth
By controlling the duty of the electromagnetic valve 32 and the sixth electromagnetic valve 44, the opening amounts of these electromagnetic valves can be varied.

The degree of opening of the exhaust bypass valve 41 is varied by varying the amount of bleed (leakage) of supercharged air introduced into the diaphragm chamber 42 a of the actuator 42 into the atmosphere by duty control of the fifth solenoid valve 32. It is variable. The degree of opening of the waste gate valve 31 is determined by the amount of bleed (leak) of the supercharged air introduced into the diaphragm chamber 9 b of the actuator 9 to the sixth electromagnetic valve 4.
It can be varied by varying the duty by the duty control of No. 4.

Engine control computer 29
Is electrically connected to sensors for detecting various operating conditions of the engine, and receives signals from the various sensors. The engine operating condition detecting sensors include an intake pipe pressure sensor 30, a throttle opening sensor 5, an air flow meter 24 as an intake air amount measuring sensor, an engine speed sensor 50, and an oxygen sensor 19. The engine control computer 29 includes a central processor unit (CPU) for performing calculations, a read-only memory (ROM) as a read-only memory, a random access memory (RAM) for temporary storage, and an input / output interface (I
/ O interface), and an A / D converter for converting analog signals from various sensors into digital quantities.

FIG. 2 is a system diagram of an engine centered on the fuel vapor control device. In the figure, reference numeral 61 denotes a fuel tank mounted on a vehicle. The fuel vapor generated in the fuel tank 61 is guided to a charcoal canister 63 through a passage 62. As is well known, the charcoal canister 63 is an adsorption container for evaporative fuel containing activated carbon, and the evaporative fuel from the fuel tank 61 is temporarily adsorbed on the activated carbon of the charcoal canister 63. To the charcoal canister 63, two purge passages, a main purge passage 64 and a sub-purge passage 65, are connected.

The downstream end of the sub-purge passage 65 is connected upstream of the compressor 7b of the main turbocharger 7. In the sub-purge passage 65, a first vacuum control valve (VCV1) 66 is interposed. First
The vacuum control valve 66 is driven to open and close by a diaphragm type actuator 66a. The supercharging pressure on the downstream side of the compressor 7b is guided to the diaphragm chamber of the actuator 66a via the passage 67. Main purge passage 64
Is connected to the surge tank 2. In the main purge passage 64, a second vacuum control valve (VCV2) 69 and a purge solenoid valve 70 are interposed. The second vacuum control valve 69 and the purge solenoid valve 70 are connected in series. The second vacuum control valve 69 is opened and closed by a diaphragm type actuator 69a. When the throttle is fully closed, a negative pressure immediately downstream of the throttle valve 4 is guided to the actuator 69a via the passage 71, so that the second vacuum control valve 69 closes. The purge solenoid valve 70 has a function of controlling the purge amount of the evaporated fuel flowing through the main purge passage 64 by changing the duty ratio by the engine control computer 29.

As shown in FIG. 1, the engine control computer 29 includes a GN detecting means 81, a duty control means 82, a throttle opening change amount detecting means 83, and a purge delay means 84. GN detection means 8
1 has a function of calculating an intake air amount (GN) per one rotation of the engine based on signals from the air flow meter 24 and the engine speed sensor 50. Duty control unit 82, based intake air amount of the engine rotational speed NE and the engine per revolution and (GN) to obtain the duty ratio of the purge solenoid valve 70 from the duty ratio map M ₁ shown in FIG. 5, an electromagnetic purge It has a function of controlling the duty of the valve 70. Throttle opening change amount detecting means 8
Reference numeral 3 has a function of obtaining an opening change amount of the throttle valve 4 with respect to time based on a signal from the throttle opening sensor 5. That is, the throttle opening change amount detecting means 83
Has a function of obtaining the valve opening speed of the throttle valve 4.
Delay means 84 on the basis of the opening degree change amount signal from the throttle opening change amount detecting means 83 has a function of delaying the purge start timing of the purge solenoid valve 70 determine the delay time from the map M ₂ shown in FIG. 6 . Each of the above means 81, 82,
83 and 84 are engine control computers 29
It is composed of programs stored in.

Next, the operation of the above evaporative fuel control system for an engine will be described. In the high intake air amount range, both the intake switching valve 18 and the exhaust switching valve 17 are opened,
The intake bypass valve 10 is closed. As a result, the two turbochargers 7, 8 are driven, a sufficient amount of supercharged air is obtained, and the output is improved. At low speed and high load, both the intake switching valve 18 and the exhaust switching valve 17 are closed, and the intake bypass valve 33 is opened. As a result, only one turbocharger 7 is driven. The reason why one turbocharger is used in the low intake air amount range is that one turbocharger supercharging characteristic is superior to two turbocharger supercharging characteristics in the low intake air amount region. By using one turbocharger, the boost pressure and the rise of torque are quickened, and the response is quick. When shifting from the low intake air amount region to the high intake air amount region, that is, when switching from one turbocharger to two turbocharger operation, the exhaust bypass valve is provided when the intake switching valve 18 and the exhaust switching valve 17 are closed. 41 is controlled to be small opening by duty control, and the intake bypass valve 33 is closed to increase the approach rotation speed of the auxiliary turbocharger 8,
Switching of the turbocharger can be performed more smoothly (shock during switching is reduced).

When the vehicle is accelerated from the fully closed state of the throttle valve 4, the air flow meter 24 indicates the amount of intake air required by the engine and the volume of the intake passage (the intake passage between the air cleaner 23 and the throttle valve 4). Instantaneously flows. Therefore, the engine speed (N
If the purge control of the evaporated fuel is performed based on E) and the intake air amount per one revolution of the engine (GN), the purge amount increases more than necessary. Therefore, in the present embodiment, the control process shown in FIG. 4 is executed. By addressing this. In step 100 of FIG. 4, the purge flow rate control routine is started, and the routine proceeds to step 101, where it is determined whether or not the engine is in a post-start state. Here, if it is determined that the state is not the state after engine start, the routine proceeds to step 110, where the duty ratio of the purge solenoid valve 70 is set to 0%, and the purge solenoid valve 70 is closed. Therefore, in this state, purging of the fuel vapor from the charcoal canister 63 to the surge tank 2 is not performed. If it is determined in step 101 that the engine is in the post-start state, the routine proceeds to step 102, where it is determined whether or not the throttle valve 4 is open. That is, it is determined whether or not the engine is in an idling operation state. If it is determined that the throttle valve 4 has not been opened, the routine proceeds to step 110, where the purge solenoid valve 70 is closed, and the purge of the evaporated fuel is not performed.

In step 102, the throttle valve 4
Is determined to be open, the routine proceeds to step 103, where the engine speed (NE) is taken into the engine control computer 29. When this process is completed, the routine proceeds to step 104, where the intake air amount (GN) per one revolution of the engine is calculated by the engine control computer 2.
9 is taken. When this processing is completed, step 10
Proceed to 5, the duty ratio is determined from the duty ratio map M ₁ based on the engine rotational speed (NE) and the engine 1 intake air amount per rotation (GN). When the duty ratio is obtained, the routine proceeds to step 106, where the throttle opening change amount detecting means 83 calculates the opening change amount ΔTA of the throttle valve 4 with respect to time.

When the opening change amount ΔTA of the throttle valve 4 is calculated in step 106, the map M shown in FIG.
The purge start timing of the purge solenoid valve 70 is calculated by the delay means 84 having ₂ . When this process ends,
Proceeding to step 108, after the delay time calculated in step 107 has elapsed, purging by the purge solenoid valve 70 is started. When the purge by the purge solenoid valve 70 is started, the process proceeds to step 109, where the duty control of the purge solenoid valve 70 is performed based on the map of FIG. When this process is completed, a series of processes is completed, and the process proceeds to step 111 and returns.

In the above process, when the throttle valve 4 is opened, the atmospheric pressure or positive pressure immediately upstream of the throttle valve 4 is guided to the actuator 69a of the second vacuum control valve 69, and the spring force is applied. The second vacuum control valve 69 is opened.
Therefore, when the pressure inside the surge tank 2 is negative, the evaporated fuel adsorbed by the charcoal canister 63 is guided to the surge tank 2 via the main purge passage 64, and the purge amount of the evaporated fuel at this time is equal to the purge amount. It is controlled by duty control of the solenoid valve 70. Thus, the main purge passage 64 has a function of performing the purge only in the low and middle intake air amount ranges. Further, at the time of transition when accelerating from the fully closed state of the throttle valve 4, the delay time from the map M ₂ in accordance with the opening degree variation ΔTA of the throttle valve 4 is required, the purge of the evaporative fuel by the purge solenoid valve 70 Start delayed. Therefore, there is no influence of the intake air amount corresponding to the volume of the intake passage. Therefore,
The increase in the purge amount of the evaporated fuel due to the increase in the duty ratio of the purge solenoid valve 70 is eliminated, and the occurrence of engine stall and misfire is prevented. The main purge passage 6
4, the reason why the vacuum control valve 69 is provided in series with the purge solenoid valve 70 is that when the purge solenoid valve 70 is open and fails, the evaporated fuel is purged and the empty This is because the fuel ratio may be overrich. Thus, the vacuum control valve 69 functions as a fail-safe.

When the pressure inside the surge tank 2 becomes positive,
The main purge passage 64 is closed by closing the second vacuum control valve 69. In this state, a positive pressure is introduced to the actuator 66a of the first vacuum control valve 66, and the sub-purge passage 65 is opened by opening the first vacuum control 66.
When the sub-purge passage 65 is opened, the fuel vapor adsorbed by the charcoal canister 63 is removed from the sub-purge passage 6.
The fuel gas is guided to the upstream of the compressor 7b of the main turbocharger 7 through 5 to purge the fuel vapor. Thus, the sub-purge passage 65 has a function of purging the fuel vapor only in the high intake air amount region. In this embodiment, the example in which the evaporative fuel device is applied to a two-stage twin turbo engine is shown, but it is of course possible to apply the present invention to an engine with a supercharger or an engine without a supercharger.

[0025]

According to evaporative fuel control system for an engine according to the present invention, depending on the opening change amount from the throttle opening change detecting means for detecting an opening degree change amount of the acceleration when the throttle valve
Delaying the purge increase start timing of the purge solenoid valve Te
Because, even during acceleration, it is not affected by the intake air amount corresponding to the volume fraction of the intake passage. Therefore, it is possible to prevent the purge amount of the evaporated fuel from being increased more than necessary, and to prevent the occurrence of engine stall and misfire due to rough air-fuel ratio. Further, by eliminating the rough air-fuel ratio, the exhaust gas purification performance can be improved, and the drivability can be improved.

[Brief description of the drawings]

FIG. 1 is a block diagram of an evaporative fuel control device for an engine according to one embodiment of the present invention.

FIG. 2 is a system diagram of an evaporative fuel control device for an engine according to one embodiment of the present invention.

FIG. 3 is a control system diagram of the engine of FIG. 2;

FIG. 4 is a flowchart showing a processing procedure of evaporative fuel control by the apparatus of FIG. 2;

FIG. 5 is a map diagram for obtaining a duty ratio of a purge solenoid valve in the apparatus of FIG. 2;

FIG. 6 is a map diagram for obtaining a purge delay time of a purge solenoid valve in the apparatus of FIG. 2;

FIG. 7 is a characteristic diagram showing a relationship between a throttle opening and a duty ratio of a purge solenoid valve in a conventional device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Engine 2 Surge tank 5 Throttle opening sensor 7 Main turbocharger 8 Sub turbocharger 24 Air flow meter 29 Engine control computer 50 Engine speed sensor 61 Fuel tank 63 Charcoal canister 64 Main purge passage 65 Subpurge passage 70 Purge solenoid valve 81 GN Detecting means 82 Duty control means 83 Throttle opening change amount detecting means 84 Purge delay means

Continuation of front page (58) Field surveyed (Int. Cl. ⁶ , DB name) F02M 25/08 301

Claims (1)

(57) [Claims] A purge solenoid valve is provided in the middle of a purge passage for guiding fuel vapor generated from a fuel tank to an intake passage downstream of a throttle valve, and the opening degree of the purge solenoid valve is determined by the amount of intake air per one revolution of the engine. throttle opening change for detecting the in evaporative fuel control system of purge flow adjustment <br/> to Rue engine to the intake passage of fuel vapor, the opening degree change amount of the throttle valve by duty control in accordance with the A delay time of the purge increase start is set according to the magnitude of the opening change amount from the amount detection means and the throttle opening change amount detection means during acceleration.
After the elapse of the delay time, the opening degree of the purge solenoid valve is increased.
And a purge delay means.